This invention is generally related to electronic imaging and more particularly to digital cameras.
The digital camera has recently been developed as a portable system that acquires and stores digital still images in electronic form. The images may be used in a number of different ways, such as being displayed in an xe2x80x9celectronicxe2x80x9d photo album or used to embellish graphical computer applications. The digital camera has a user interface much like a conventional chemical film camera, but the images are captured and stored entirely using electronic solid state circuitry and image processing techniques.
A typical digital camera has an electronic image sensor that receives incident light reflected from an object or scene through an optical interface. The optical interface may include a lens system, an aperture mechanism, and perhaps a light filter. The sensor can typically be implemented as an array of charge coupled device (CCD) or complimentary metal oxide semiconductor (CMOS) photodetecting circuits that create light-generated signals in response to the incident light. Analog signals from the sensor are converted into digital format by an analog-to-digital (A/D) converter and are then further processed by logic circuitry and/or a programmed processor to yield a captured digital image of the object or scene. The image may then be stored in local memory aboard the camera. In addition, the image may be transferred to a computer that is linked to the digital camera, for storage as an electronic file and/or for further graphical and image processing to improve the image quality or use with graphics software.
Most purchasers of digital cameras have access to a desktop computer for viewing the still images. Therefore, such purchasers might also enjoy using their digital camera to communicate with another person, such as in videoconferencing with a desktop computer in order to both see and hear the other person. However, most digital cameras are typically configured to provide only still images. Similarly, cameras used for videoconferencing do not operate as a still camera when disconnected from the computer. Therefore, there is a need for a digital camera and associated image processing architecture that permits xe2x80x9cdual modexe2x80x9d use of the camera for both video, where the camera may be linked to a desktop computer for video purposes, and still image capture.
The invention is directed at a method of configuring a signal processing system to operate in one of at least two modes to yield video and still image data, a first mode for processing image sensor signals according to a first selection of signal processing methodologies, to obtain still image data, and a second mode for processing the same image sensor signals according to a second selection of signal processing methodologies, to obtain video image data.
In a particular embodiment of the invention, the signal processing methodologies include image scaling, decorrelation, and entropy encoding that are performed sequentially to yield video or still data from the same original image data. The first selection of scaling, decorrelation, and encoding is designed to provide video data, whereas the second selection is designed to provide data for still images which would normally have greater size and detail than the video images. In a preferred embodiment, the system yields video or still data depending on the parameters loaded into look-up-tables (LUTs) that are used to configure logic circuitry for performing the image decorrelation and entropy encoding.